According to Vinnie Cilurzo you drill a 7/64 hole in the barrel head and insert the nail. He says you can do it empty or full (just be quick with the nail) since it is so small you don't loose much.

I double checked the nail diameter with my micrometer and it was 7/64 also! This made me a little unsure especially since my barrel was full of 3 month old RIS. However I figured if Vinnie Cilurzo says it will work then I'm doing it.

Below is a picture with the nail inserted. Believe it or not its pretty snug. Actually I had to use a claw hammer to pull the nail after I inserted it by hand.

They can be obtained from McMaster Carr. Unfortunately you have to buy a box which is around $22 plus shipping. I was fortunate enough to have a member who bought a box send me a couple.

This is a reply from Vinnie Cilurzo taken from another site. Hope this helps!

Quote:

Here is the info on the stainless steel nail in the barrel head acting as a
poor man’s MacGyver sample port:

We drill a hole using a 7/64 drill bit on the barrel head of each barrel.
The hole can be drilled while the barrel is empty or even with beer in it.
You just have to be ready with the nail if you are doing it with the barrel
full. The hole is so small that there is no problem with losing too much
beer at this point.

I have two sizes of stainless steel nails that I purchase from McMaster
Carr.

I use the smaller nail, but, I keep the larger ones around just in case a
hole gets boarded out to large, it hasn’t happened yet, but, I’m just
playing it safe.

I do use barrel wax sometimes (www.barrelbuilders.com) around the nail after
I have pulled a sample. We have never had a nail blow out due to pressure;
they are pretty snug in there.

You can pull a sample and actually have the flow stop coming out of the
small hole in the head of the barrel because the barrel is not vented, but,
there is no issue. It is such a small hole that you can’t harm the barrel.
If anything, it makes it easier because you can control the flow by removing
the bung and putting it back into place. I usually drill the hole about
half way up on the barrel head.

Recently we've started to drill the barrel out after the barrel has beer in
it as opposed to before. Sometimes you don't get the small hole drilled out
all the way. You won't know that this is the case until there is beer in
the barrel and you see that you don't even have a small stream of beer
coming out of the hole.

I've also taken to the practice of having a backup nail in my pocket when
I'm pulling samples just in case you drop the nail on the floor on accident.

The hole at the bottom of the head of the barrel (six o’clock if you are
looking at the head of the barrel straight on) for removing beer with fruit
in it is a 15/16” hole, the tubing that you use to remove the liquid and
fruit is also from McMaster Carr. A Belgian beer bottle cork like we cork
with fits in the 15/16” hole. Here is the part number from McMaster for the
tubing:

15/16” OD tubing, McMaster Carr # 5231K944

It takes a little practice but you can removing the cork quickly and push
the 15/16” tubing in the cork hole. The tubing is than run down to some
sort of strainer that you would need to fashion and from the strainer it is
pumped to a tank.

Why can't you just open up the bung at the top of the barrel and draw a sample with a sanitized turkey baster or wine thief? That's what I do.

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The idea is for sour beers where you don't want to break the protective pectile/bellicum that has formed a barrier on top of the beer. Pull the nail below the line to get a sample. I'd also think that it would reduce the likelihood of airborne particulates falling down in through the bung hole. The nail has positive pressure to push it all out in to your sample.